Role of sodium and volume in the pathogenesis of hypertension in dialysis patients. Reflections on pathophysiological mechanisms

Chest Ultrasound as a New Tool for Assessment of Volume Status in Hemodialysis Patients

Accurate assessment of volume status (VS) in hemodialysis (HD) patients is challenging. The use of chest ultrasound (CUS) for detection of extravascular lung water has recently gained wide acceptance. The aim of this study was to evaluate the use of CUS in VS assessment in HD patients in comparison to clinical and inferior vena cava (IVC) indices and to assess their relation with volume displacement after ultrafiltration. This prospective cohort study was carried out on 38 patients on regular HD. VS was assessed using a 13-point clinical score, and IVC indices and CUS score were measured pre- and post-ultrafiltration. Correlation between these parameters and with ultrafiltration volume was tested. There was a statistically significant reduction in post-ultrafiltration CUS score and the 13-point clinical score (P < 0.01). Moreover, reduction in all the IVC indices (inspiratory and expiratory diameters and collapsing index) was detected, but did not reach statistical significance (P = 0.185, P = 0.296, and P = 0.194, respectively). CUS score had statistically significant correlations with ultrafiltration volume and New York Heart Association classes (P < 0.001 and <0.001, respectively). Neither clinical signs nor IVC indices can be used independently for the assessment of VS in HD patients. CUS is a useful guide in VS assessment, and we recommend its routine use in the management of HD patients. Concomitant use of bio- impedance analysis (BIA) may be needed in addition to CUS for more accurate assessment of VS in HD patients.

Single-dwell treatment with a low-sodium solution in hypertensive peritoneal dialysis patients

BACKGROUND

Patients on peritoneal dialysis (PD) may suffer from sodium (Na) and fluid overload, hypertension and increased cardiovascular risk. Low-Na dialysis solution, by increasing the diffusive removal of Na, might improve blood pressure (BP) management.

METHODS

A glucose-compensated, low-Na PD solution (112 mmol/L Na and 2% glucose) was compared to a standard-Na solution (133 mmol/L Na and 1.5% glucose) in a prospective, randomised, single-blind study in hypertensive patients on PD. One daily exchange of the standard dialysis regimen was substituted by either of the study solutions for 6 months. The primary outcome (response) was defined as either a decrease of 24-h systolic BP (SBP) by ≥6 mmHg or a fall in BP requiring a medical intervention (e.g. a reduction of antihypertensive medication) at 8 weeks.

RESULTS

One hundred twenty-three patients were assessed for efficacy. Response criteria were achieved in 34.5% and 29.1% of patients using low- and standard-Na solutions, respectively (p = 0.51). Small reductions in 24 h, office, and self-measured BP were observed, more marked with low-Na than with standard-Na solution, but only the between-group difference for self-measured SBP and diastolic BP was significant (p = 0.002 and p = 0.003). Total body water decreased in the low-Na group and increased in the control group, but between-group differences were not significant. Hypotension and dizziness occurred in 27.0% and in 11.1% of patients in the low-Na group and in 16.9% and 4.6% in the control group, respectively.

CONCLUSIONS

Superiority of low-Na PD solution over standard-Na solution for control of BP could not be shown. The once daily use of a low-Na PD solution was associated with more hypotensive episodes, suggesting the need to reassess the overall concept of how Na-reduced solutions might be incorporated within the treatment schedule.

Residual Renal Function and Effect of Low-Sodium Solution on Blood Pressure in Peritoneal Dialysis Patients

Background:Residual renal function (RRF) affects sodium and fluid balance. The aim of this analysis was to examine the impact of RRF on the effect of a sodium-reduced peritoneal dialysis fluid (PDF) on blood pressure (BP).Methods:This is a post-hoc analysis of a prospective, randomized, controlled double-blind clinical trial with 82 patients on continuous ambulatory PD (CAPD) treated with a low-sodium (125 mmol/L Na) or a standard-sodium (134 mmol/L Na) PDF. Subgroups according to glomerular filtration rate (GFR) at baseline (≤ / > 6 mL/min/1.73 m²) were analyzed for BP and antihypertensive medication.Results:In the low-GFR group on low-sodium PDF (N = 26), systolic BP was reduced from 152 ± 24 mmHg at baseline to 137 ± 21 mmHg at week 12, diastolic BP from 90 ± 16 mmHg to 83 ± 11 mmHg. In the low-GFR group on standard-sodium PDF and in the high-GFR group on both PDF types, only minor changes were observed. For the low-GFR subgroup, the confounder-adjusted mean study group difference in systolic BP at week 12 between low-sodium and standard-sodium PDF was -16.9 (95% confidence interval [CI] -27.2 to -6.6) mmHg, for diastolic BP, it was -7.0 (95% CI -12.6 to -1.4) mmHg. In both GFR subgroups, more patients had a reduced daily dose of antihypertensive medication and fewer patients an increased daily dose in the low-sodium compared with the standard-sodium group at week 12.Conclusions:The reduction of BP with a sodium-reduced PDF seems to be more effective in patients with no or low RRF than in patients with residual capacity of renal sodium and fluid control.

Effect of Strict Volume Control on Renal Progression and Mortality in Non-Dialysis-Dependent Chronic Kidney Disease Patients: A Prospective Interventional Study

OBJECTIVE

The aim of this study was to examine the effect of volume status on the progressions of renal disease in normovolemic and hypervolemic patients with advanced non-dialysis-dependent chronic kidney disease (CKD) who were apparently normovolemic in conventional physical exam-ination.

MATERIALS AND METHODS

This was a prospective interventional study performed in a group of stage 3-5 CKD patients followed up for 1 year. Three measurements were made for volume and renal status for every patient. The fluid status was assessed by a bioimpedance spectroscopy method. A blood pressure (BP) value > 130/80 mm Hg prompted the initiation or dose increment of diuretic treatment in normovolemic patients.

RESULT

Forty-eight patients (48%) were hypervolemic. At the end of the 1-year follow-up, hypervolemic patients were found to have a significantly lower estimated glomerular filtration rate and higher systolic BP compared to baseline. Hypervolemia was associated with an increased incidence of death.

CONCLUSION

We have shown that maintenance of normovolemia with diuretic therapy in normovolemic patients was able to slow down and even improve the progression of renal disease. Volume overload leads to an increased risk for dialysis initiation and a decrease in renal function in advanced CKD. Volume overload exhibits a stronger association with mortality in CKD patients.

Evaluation of Salt Intake, Urinary Sodium Excretion and Their Relationship to Overhydration in Chronic Kidney Disease Patients

The purpose of this study was to estimate sodium intake in a group of patients with chronic kidney disease (CKD) and to correlate the results with the urinary excretion values of sodium and signs of fluid overload. We included patients with CKD in different stages. Urinary sodium was measured in 24 h urine samples. Body composition monitor (BCM) was used to estimate the hydration status. Sixty patients (38 ± 15 ml/min of GFR) presented 4.14 ± 1.71 g/24 h of urinary sodium excretion. Overhydration was detected in 50% of the patients by the BCM. There was a positive correlation between the measured sodium excretion values and BCM, ICW, ECW and TBW. In conclusion, markers of overhydration evaluated by BCM were positively correlated with urinary sodium excretion.

The gut microbiome, kidney disease, and targeted interventions

The human gut harbors >100 trillion microbial cells, which influence the nutrition, metabolism, physiology, and immune function of the host. Here, we review the quantitative and qualitative changes in gut microbiota of patients with CKD that lead to disturbance of this symbiotic relationship, how this may contribute to the progression of CKD, and targeted interventions to re-establish symbiosis. Endotoxin derived from gut bacteria incites a powerful inflammatory response in the host organism. Furthermore, protein fermentation by gut microbiota generates myriad toxic metabolites, including p-cresol and indoxyl sulfate. Disruption of gut barrier function in CKD allows translocation of endotoxin and bacterial metabolites to the systemic circulation, which contributes to uremic toxicity, inflammation, progression of CKD, and associated cardiovascular disease. Several targeted interventions that aim to re-establish intestinal symbiosis, neutralize bacterial endotoxins, or adsorb gut-derived uremic toxins have been developed. Indeed, animal and human studies suggest that prebiotics and probiotics may have therapeutic roles in maintaining a metabolically-balanced gut microbiota and reducing progression of CKD and uremia-associated complications. We propose that further research should focus on using this highly efficient metabolic machinery to alleviate uremic symptoms.

The Great East Japan Earthquake affected the laboratory findings of hemodialysis patients in Fukushima

BACKGROUND

The aim of the present study was to investigate the impact of the Great East Japan Earthquake on laboratory findings in chronic hemodialysis (HD) patients in Fukushima.

METHODS

Changes in laboratory findings and cardiothoracic ratio (CTR) between before and after the earthquake were retrospectively analyzed in 90 adult HD patients with end-stage renal disease (ESRD). Two hospitals located within 80 km from the Fukushima Daiichi Nuclear Power Plant, where American government recommended to evacuate from the area, participated in the study. HD duration was shortened by 0.5-1 hour for 1 month after the earthquake. Multivariate analyses were performed to identify the factors contributing to change of measurement values.

RESULTS

Blood urea nitrogen (BUN) value was significantly transiently decreased for 1-2 weeks after the earthquake (P=0.002). In multivariate analysis, age showed a tendency to be related to the decrease of BUN level (P=0.05). Hematocrit value was significantly elevated after two months compared with that at baseline (P=0.02), although the elevation was small. The other measured values and CTR were not significantly changed compared with those before the earthquake.

CONCLUSIONS

Laboratory findings and CTR did not worsen despite the shortening of HD duration. Hence, in this disaster, as far as chronic HD patients with ESRD were concerned, it was possible for the duration of HD treatment to be safely decreased.

Body weight telemetry is useful to reduce interdialytic weight gain in patients with end-stage renal failure on hemodialysis

Lacking compliance with liquid intake restrictions is one of the major problems in patients on hemodialysis and causes an increased mortality. In 120 patients on hemodialysis with an average interdialytic weight gain (IWG) exceeding 1.5 kg on at least 2 days during the 4 weeks preceding the intervention, the effect of telemetric body weight measurement (TBWM) on IWG, ultrafiltration rate, and blood pressure was evaluated over a period of 3 months. Patients of the telemetric group (TG) were supplied with automatic scales, which transferred the weight via telemetry on a daily basis. In the case of IWG of more than 0.75 kg/24 h, a telephonic contact was made as required, and in the case of an IWG of more than 1.5 kg, telephonic contacting was obligatory along with the advice of a liquid intake restriction to 0.5 L/day until the next dialysis. The patients of the control group (CG) received standard treatment without telemetric monitoring. We examined specific data of the second interdialytic interval (IDI2) and the average within 1 week. The average difference of IWG between TG and CG was not significant before the start of the study but 0.2 kg (p=0.027) (IDI2)/0.27kg (p=0.001) (WP) at the end of the study, respectively. The average difference in the ultrafiltration rate within 1 week was 19.0 mL/h (p=0.282) (IDI2)/8.2 mL/h (p=0.409) before the start of the study but 28.4 mL/h (p=0.122) (IDI2)/30.9 mL/h (p=0.004) at the end of the study, respectively. Thus, TBWM is a feasible method for optimizing the IWG and reducing the ultrafiltration rate.

Dialysis adequacy today: a European perspective

The need to improve haemodialysis (HD) therapies and to reduce cardiovascular and all-cause mortality frequently encountered by dialysis patients has been recognized and addressed for many years. A number of approaches, including increasing the frequency versus duration of treatment, have been proposed and debated in terms of their clinical efficacy and economic feasibility. Future prescription of dialysis to an expanding end-stage chronic kidney disease (CKD-5D) population needs a re-evaluation of existing practices while maintaining the emphasis on patient well-being both in the short and in the long term. Efficient cleansing of the blood of all relevant uraemic toxins, including fluid and salt overload, remains the fundamental objective of all dialysis therapies. Simultaneously, metabolic disorders (e.g. anaemia, mineral bone disease, oxidative stress) that accompany renal failure need to be corrected also as part of the delivery of dialysis therapy itself. Usage of high-flux membranes that enable small and large uraemic toxins to be eliminated from the blood is the first prerequisite towards the aforementioned goals. Application of convective therapies [(online-haemodiafiltration (OL-HDF)] further enhances the detoxification effects of high-flux haemodialysis (HF-HD). However, despite an extended clinical experience with both HF-HD and OL-HDF spanning more than two decades, a more widespread prescription of convective treatment modalities awaits more conclusive evidence from large-scale prospective randomized controlled trials. In this review, we present a European perspective on the need to implement optimal dialysis and to improve it by adopting high convective therapies and to discuss whether inertia to implement these practice patterns may deprive patients of significantly improved well-being and survival.

Blood pressure measurements and left ventricular mass index in hemodialysis patients

Left ventricular hypertrophy (LVH) is the most frequent cardiac abnormality in hemodialysis (HD) patients. It is related to cardiovascular diseases and is an important risk factor for mortality in HD patients. Arterial hypertension is an established risk factor for LVH in HD patients. Inferior vena cava (IVC) diameter is a good indicator of circulating fluid volume; hypervolemia is an important pathogenetic factor of hypertension in HD patients. The purpose of our study was to evaluate possible association between LVH, IVC diameter, and different blood pressure (BP) measurements in HD patients. In the present study, 85 HD patients were included. BP was measured with a standard mercury sphygmomanometer before and after the HD session; the average 1-monthly values of the routine BP measurements were also analyzed. 24- and 48-h ambulatory blood pressure measurements (ABPMs) were performed after the end of HD sessions using a noninvasive ABPM. Average values of systolic and diastolic BP were analyzed separately for the first (HD) and second (interdialytic) day ABPM and for both days together. Using echocardiography, left ventricular mass was measured and left ventricular mass index (LVMI) was calculated. Using ultrasonography, IVC diameter was measured on the interdialytic day. Using multiple regression analysis, we found statistically significant correlations between LVMI and mean monthly postdialysis systolic BP (P < 0.05) and mean 48-h diastolic BP (P < 0.05). Only longer BP measurements (average 1-month post-HD and 48-h ABPM) were associated with LVMI in HD patients.

Blood pressure and heart rate variability in patients on conventional or sodium-profiling hemodialysis

BACKGROUND

Autonomic nervous system dysfunction and dialysate sodium (Na) concentration are believed to play a role in the pathogenesis of hemodialysis-related hypertension. The present study was undertaken to determine whether increases in blood pressure in hemodialysis patients are associated with changes in heart rate variability (HRV), a measure of the autonomic nervous system function, and long-term exposure to increased dialysate Na concentration.

METHODS

Baseline clinical, biochemical data and HRV of patients undergoing increased Na profiling dialysis (High-Na, n = 9) and on conventional treatment (Control, n = 11) were compared with those obtained after one year of study.

RESULTS

After one year, the mean predialysis systolic blood pressure (SBP) increased in seven patients of the High-Na and in five of the Control group, and decreased or remained unchanged in the remaining subjects. Initial HRV was significantly higher in patients with increased SBP, and it increased further in these patients after one year. At the end of the study, post-dialysis plasma Na, osmolality, and weight gains were significantly higher in the High-Na group. No significant correlation, however, was found between individual changes in intradialytic sodium elimination and the alterations in blood pressure.

CONCLUSION

These data suggest that the dialysate sodium concentration, a most important determinant of interdialytic weight gain and fluid balance, is only partly correlated with long-term changes in blood pressure. An increased blood pressure over time may develop in a subset of hemodialysis patients with higher HRV, suggestive of increased sympathetic activity.

Acquired cystic kidney disease and arterial hypertension in hemodialysis patients

BACKGROUND

Acquired cystic kidney disease (ACKD) and arterial hypertension (AH) are both frequent complications in hemodialysis (HD) patients. Until now, AH has not been described as a complication of ACKD.

PATIENTS AND METHODS

Our study included 86 HD patients (46 men and 40 women; mean age 51.3 years; mean duration of HD treatment 55.3 months). Their native kidneys were examined with an ATL-HDI 3000 ultrasound device (2-4 MHz convex probe). Depending on the number of cysts in the kidney, the manifestations were divided into three grades: grade 0: no cysts; grade 1: fewer than ten cysts in both kidneys; grade 2: more than ten cysts in both kidneys. Blood pressure was measured 30 minutes before and after HD. Mean one-month values were analyzed. AH was defined as systolic blood pressure > or = 150 mmHg, diastolic blood pressure > or = 90 mmHg and/or antihypertensive treatment. The diameter of the inferior vena cava (indicator of dry weight) was measured with the same ultrasound device as the kidneys three hours after HD.

RESULTS

ACKD was present in 48 (55.8%) patients, there was no statistically significant difference regarding sex. Twenty-four (50%) patients had grade 1 ACKD and 24 (50%) grade 2 ACKD. Sixty-eight (79.1%) patients suffered from AH, which was significantly more common among the men (P = 0.048). AH was detected before HD in 68 (79.1%) patients and in 54 (62.8%) patients also after HD. Thirty-nine (45.3%) patients suffered simultaneously from ACKD and AH; 22 (56.4%) of them were men and 17 (43.6%) women. No significant correlation between AH and ACKD was established. The prevalence and grade of ACKD were significantly associated with the duration of dialysis treatment (P < 0.01). Multiple regression analysis detected a significant correlation only between AH and the diameter of the inferior vena cava (P < 0.05).

CONCLUSIONS

ACKD is common in HD patients. Its prevalence and grade increase with the duration of dialysis treatment. ACKD is not associated with AH. There is a correlation between the diameter of the inferior vena cava, as a factor of circulating fluid volume, and AH in HD patients.

Associations between renal function, volume status and endotoxaemia in chronic kidney disease patients

Inflammation is an important predictor of increased cardiovascular morbidity and mortality in patients with chronic kidney disease (CKD), but the mechanisms behind the chronic activation of the immune system are not clearly understood. CKD patients develop fluid overload, which has been proposed to be a stimulus for inflammatory activation due to the translocation of macromolecules from the gut. We hypothesize that fluid overload is associated with signs of systemic inflammation and endotoxaemia in stages 1-5 CKD patients. The aim of this prospective study was to evaluate the associations between renal function, fluid status [evaluated by the inferior vena cava diameter (IVCD) and the collapsibility index (CI)], systemic inflammation [plasma levels of C-reactive protein (CRP), fibrinogen and albumin] and endotoxaemia (through the Limulus amebocyte lysate enzymatic assay) in a group of CKD patients in our out-patient clinic. The population consisted of 74 (mean of 57; range 23-83 years of age; 47% males) CKD patients with glomerular filtration rate (based on the mean of urea and creatinine clearances) of 34 ml/min. Both albumin (Rho = 0.25; P = 0.05) and fibrinogen (Rho= - 0.48; P < 0.0001) were significantly correlated to glomerular filtration rate (GFR). According to the IVCD, 84% of the patients were fluid overloaded, while 83% were considered overloaded by the CI. Signs of endotoxaemia were detected in all patients. Endotoxin levels were higher in patients with signs of fluid overload (0.85 +/- 0.11ng/l) when compared with patients with normal values of IVCD (0.61 +/- 0.05 ng/l; P < 0.05). Endotoxin levels correlated to both IVCD (Rho=0.33, P < 0.005) and CI (Rho = -0.25, P < 0.05). There was no correlation between endotoxin levels and GFR, CRP or fibrinogen. In summary, although most CKD patients presented signs of fluid overload that was associated with endotoxaemia, there was no association between endotoxaemia and systemic inflammation, suggesting the endotoxaemia may not be the main determinant of the inflammatory status in this group of patients.

Residual Renal Function and Volume Control in Peritoneal Dialysis Patients

BACKGROUND

Fluid overload is not uncommon in patients on continuous ambulatory peritoneal dialysis (CAPD). Previous studies suggested that residual renal function (RRF) played an important role in maintaining fluid balance. However, good fluid status should be a balance between fluid intake and removal. Therefore, in the present study, we investigated the effect of RRF on patients' fluid status after focusing on the balance between fluid intake and removal in CAPD patients.

METHODS

In this cross-sectional study, 195 stable CAPD patients in a single center were included. Patients were divided into three groups according to their urine output: anuric group with urine < or =100 ml/day, oliguric group with urine < or =400 ml/day and UO >400 ml group with urine >400 ml/day. Fluid status was evaluated by bioimpedance analysis and mean arterial pressure (MAP). The sodium removal and plasma sodium concentration were also measured. All the patients were educated to try to achieve good volume control by focusing on salt and fluid intake and their removals.

RESULTS

There were 51, 31 and 113 patients in anuric, oliguric and UO >400 ml group, respectively. Anuric patients were older and had been on CAPD longer than that of the oliguric and UO >400 ml patients (p < 0.05). The urine output in the three groups were 9.28 +/- 22.68, 236.13 +/- 75.43 and 1,013.34 +/- 541.54 ml/day, respectively (p < 0.001). Bioimpedance analysis showed that the differences of extracellular water, intracellular water and total body water were not statistically significant among the three groups. However, there was significant difference in MAP among the three groups (MAP in anuric, oliguric and UO >400 ml groups were 93.27 +/- 13.35, 96.63 +/- 9.94 and 102.36 +/- 13.70 mm Hg, p < 0.01), and UO >400 ml group had higher MAP than anuric and oliguric groups (p < 0.05). The total sodium removal (renal + peritoneal) in anuric, oliguric and UO >400 ml groups were 96.44 +/- 60.18, 98.95 +/- 73.82 and 134.64 +/- 72.44 mmol/day, respectively (p < 0.01). The UO >400 ml group also had higher plasma sodium concentration than anuric and oliguric groups (plasma sodium in the three groups were 137.49 +/- 3.43, 137.82 +/- 2.63 and 139.15 +/- 3.30 mmol/l, respectively; p < 0.01).

CONCLUSIONS

This study showed that extracellular water among anuric, oliguric and UO >400 ml groups was not significantly different, which suggested that RRF may be not so important as expected in maintaining good volume status. The higher blood pressure in patients with higher RRF and higher sodium and fluid removal in the present study suggested restricting salt and fluid intake might be more important for better blood pressure control in CAPD patients.

Pathologic Basis and Treatment Considerations in Chronic Kidney Disease-Related Hypertension

Chronic kidney disease (CKD) is both a cause and an effect of hypertension and is multifactorial in its origin. Beyond volume expansion, CKD-related hypertension is without defining characteristics of any consistency. Consequently, the order in which antihypertensive medications are given to the CKD patient with hypertension is arbitrary, although prescription practice is for the most part mindful of the need for multiple drug classes with at least one of them being a diuretic. It is not without reason that blood pressure goals in the hypertensive CKD patient are set at lower levels than those for patients with essential hypertension, but it remains to be determined how much the blood pressure should be decreased in the CKD patient.